Kryptonite

Hello, I am having trouble with some homework given to us by a professor in a BASIC Astronomy class. Describe how you would design an experiment to determine the radius of the sun, writing down equations used in each step.We have been covering Stefan-Boltzmann constant so I assume he would prefer we use this in the process. This is all the info we were given to start the assignment. I understand the equation to use are: L=(Stefan-Boltzmann Constant) * T^4 * 4(Pi)R^2 Although not sure how to find L. Again this is a BASIC Astronomy, so nothing too complex (but sadly this one is too difficult for me). Thanks in advance for the help!